While orbit numbers are generated serially in time, path numbers are determined for all the satellite ground tracks during a recurrent period in a westward direction. Therefore, a certain satellite ground track is uniquely determined by specifying a corresponding path number. One can know the observed area from the sensor swath width and incidence angle. Although one path is a revolution that begins at an equator crossing point in the ascending node, a data granule of AMSR and AMSR-E is defined as a half of a revolution ranging from pole to pole. Due to this inconsistency between the two definitions, AMSR and AMSR-E use the path number where the data granule begins. To distinguish these two numbers, hereafter we call the original number the "satellite path number" and AMSR and AMSR-E path number simply the "path number." The number used in the image archive system is this "path number." The recurrent period, total number of paths during a recurrent period, and longitude of origin are shown in Table 1 for each sensor.
Table 1@Parameters for determining path number
Satellite/Sensor
Recurrent Period
Total number of paths
Longitude of origin
ADEOS-II/AMSR
4
57
0.924W @ 57 th satellite path
Aqua/AMSR-E
16
233
64.6W @ 1 1 satellite path
The conceptual scheme for ADEOS-II/AMSR numbering path is shown in Fig. 1.
Fig. 1 Conceptual scheme for ADEOS-II/AMSR numbering path
The figure is a conceptual diagram of satellite ground tracks in the ascending node. Intervals between contiguous paths are not exactly correct in size. For the ADEOS-II/AMSR, we define the satellite path crossing at 0.924W in the ascending node as the 57th path, and sequentially increment the satellite path number in a westward direction. As shown by thick paths, the Earth surface is observed every four tracks in time series. Path numbers differ from satellite path numbers due to the origin of the path. A descending track is plotted as dashed line for reference.
